This PR was merged into the 2.1 branch.
1daefa5 [Routing] made it compatible with older PCRE version (pre 8)
[Routing] compatibility with older PCRE version (pre 8)
Ok I changed my mind about this issue.
1. I figured more people are affected than I thought and CentOS is stubborn.
2. Symfony still uses the old regex style `?P<param>` in several other components. So also doing so in the routing makes it more consistent.
3. Even if it's definitely not good to use an over 6 year old PCRE version with a recent PHP version, we can still try to provide the best experience. It doesn't mean we support outdated software stacks of custom PHP compilations as we won't and cannot specifically test against it.
@fabpot: I will do a seperate PR on master when you merged this because the code changed alot in master so it cannot easily be merged I guess. I will also convert the symfony requirement for PCRE in the requirements check to a recommendation.